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Launching - quick standing starts

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Porschester	Launching - quick standing starts		Lead	[-]
Posts: 4 09/13/06 11:58:23	Tags : None Hi there, I have a Super 7 with an old ZX-10 engine in it that me and my bro use for autocross, I'm new to the bike engined thing and was wondering your techniques on how to make the fastest start from standing. Recently we have been attempting to pop the clutch at 9,000 rpm .. this sometimes results in wheel spin and the rpm stays up .. but mostly it just bogs down the motor and the start ends up being slow. I have also tried prolonged clutch slipping at high rpm but its difficult to get right with the bike clutch and no torque. Any advice/discussion would be grateful. If possible could you share your successful technique? Porschester
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Clark Lincoln	launching	#1	[url]	[-]
Registered User Posts: 771 09/13/06 13:10:47	The closest we (bike engined SR's) come to standing starts is getting off the false grid - and that can cause problems sometimes You've got more weight (I think) so the lack of torque in these motors will make things tough - unless you don't worry about frying the clutch after a couple of burnouts. I would think gearing should help. Cark
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David Ferguson	Re: Launching - quick standing starts	#2	[url]	[-]
Registered User Posts: 1291 09/13/06 18:40:57	A quick google search found some of these gems: With a stick shift, the main aim is to avoid excessive wheelspin by pressing the throttle too much, but also avoid bogging down the motor by pressing the throttle too little. The driver has to get the throttle input just right, like in that Goldilocks fairytale. Each car engine has a different rpm range in which it will produce the most power. Launching a car hard from a dead stop is accomplished by slipping the clutch and spinning the tires, both within reason. Power is lost here, but most engines have narrow power and torque bands, so the fastest launch will include wheelspin and slipping the clutch. The only way to find out how much slipping would be just right is to experiment at the track, holding the throttle at various rpm levels at launch to see how much juice is needed for the quickest start. And... Also, try launching higher. You need to find the sweet spot, between bogging and wheelspin, and that will takes lots of practice and change from day to day, track to track, etc... The more traction you get from the tires, the higher you can launch your car, and you generally want to launch above torque peak so that when the tires grab, the tach drops, and if you can work the clutch right, avoid major wheelspin, you'll launch like a rocket. With my DR's I launch at 5500 rpm. On my OEM Dunlops more like 4500-4800 rpm at 26 psi. Gotta get the throttle steady when staging, an even rpm, clutch half in, half out, just about to grab, the tach dipping ever so slightly. When the green hits, don't slam your foot down on the gas to the floor, quickly and steadily squeeze it to the floor, and gradually but quickly let out the clutch, sense too much throttle, keep it steadily continually going down and adjust the power to the wheels with the clutch, not the gas. More thoughts.... The best possible launch is obtained by obtaining the optimal balance of applying the most amount of power to the ground with the least amount of wheel spin. If too much power is applied during the launch and the tires spin, the resulting 60 foot time will be poor. The same goes for not applying enough power, thereby causing the cars engine to bog, and having the car limp off the line slowly. When launching a car with a manual transmission come to a complete stop after the car is properly staged. Press the clutch in all the way with one foot while pressing the accelerator pedal down with the other foot, raising the engine RPM to a constant moderate level for the first launch. Lift up on the clutch pedal to the point where the car is just about to start moving and hold both pedals still. When the christmas tree lights reach the last amber before the green, slowly release the clutch while quickly applying the accelerator pedal enough to launch the car quickly, but not too much to induce a large amount of wheel spin. Start conservative with the first launch and keep increasing the RPM at which the car is launched at during the subsequent runs. If the car starts spinning the tires too much after the launch, lower the launch RPM and try again. So, in summary. Go testing. Learn the technique for releasing the clutch so the engine doesn't bog at a given RPM. Experiment with RPMs to find the combination that give the best launch.
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Jake Latham	Re: Launching - quick standing starts	#3	[url]	[-]
Registered User Posts: 446 09/13/06 19:29:46	As one data point, I launch at 8-9K, slip the clutch horribly, and feed in the throttle as fast as possible to keep the tires from spinning. No bog, minor occasional wheelspin if I try to tip in too much too soon, or am on lotsa marbles. 1100# Radical, 2003 R1, 13/50 gearing - gets going quite well. As David said - just practice a bit, you'll get used to it - no two cars will be the same. -Jake
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Dick Rasmussen	Re: Launching - quick standing starts	#4	[url]	[-]
Registered User Posts: 50 09/13/06 20:12:53	You either need to slip (smoke) the clutch or moderately spin the tires (which will put some heat in them . . . a good thing in autocross). If frequent clutch replacement isn't desireable (aka dragster slipper clutches) then your best solution may be a shorter 1st gear/final drive. I have a lot of standing start (Pro Solo and normal autocross) experience with a torquey (compared to a bike engine) FF 1600. With the "right" gearing it is pretty easy to get enough tire spin to keep from bogging the engine without smoking the tires. Fortunately the R25A tires tend to hook up well even with initial slip so the revs don't drop but the tires don't smoke. My Tilton clutch holds up very well since it is used as an "on/off" switch instead of being slipped. Dick CM 85
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